Systems and methods for in-line interference detection in point-to-point radio links

ABSTRACT

An interference detection system comprises memory storing computer instructions to cause a processor to perform gathering a temporal snapshot of radio parameter values associated with a first site of a point-to-point radio system, the radio parameter values including at least a receive signal level (RSL) value and at least one other radio parameter value correlated with signal degradation; determining whether the RSL value is greater than an RSL threshold; determining whether the other radio parameter value indicates a threshold level of signal degradation; when the RSL is greater than the RSL threshold and the other parameter indicates a threshold level of signal degradation during the temporal snapshot, determining that external interference is present during the temporal snapshot; when the RSL is not greater than the RSL threshold, determining that the external interference is not present; and performing a responsive action to a determination of the external interference being likely present.

PRIORITY CLAIM

This application claims benefit of and hereby incorporates by referenceprovisional patent application Ser. No. 63/007,526, entitled “In-LineInterference Detection Methods in Point-to-Point Microwave Links,” filedon Apr. 9, 2020, by inventors Gary Croke, Sergio Licardie, RobertVilhar, Sreco Plevel and Marius Koegelenberg.

TECHNICAL FIELD

This invention relates generally to point-to-point radio links, and moreparticularly provides systems and methods for in-line interferencedetection in point-to-point radio links.

BACKGROUND

Radio signal interference involves the presence of unwanted radiosignals that degrade, obstruct or interrupt a radio communicationservice. There are many types of interference (co-channel, adjacentchannel, steady, bursty, regular, irregular, etc.) and many levels atwhich interference can be present (strong, moderate, weak). There arealso many different conditions that could lead to interference. Some ofthem are completely intentional and expected (unlicensed bands) and someare involuntary and unpredictable (effects of multipath).

SUMMARY

Some embodiments of the invention perform in-line interferencemonitoring in point-to-point (PTP) radio links. Being able to accuratelydetermine if interference is affecting a PTP radio link is important toidentify problems and improve performance. Some embodiments may operatewhile the PTP radio link is online and without having to stop ongoingpayload transport.

Some embodiments may apply to any of the microwave frequencies availablefor wireless data transport in the United States and internationally.Some systems may be particularly useful for licensed users of the 6 GHzfrequency band in the United States where the Federal CommunicationsCommission (FCC) has decided to allow unlicensed use of the band foroperations relying on WiFi and other technical standards. The FCCproposes to allow unlicensed use in the 5.925-7.125 GHz (6 GHz) bandwhile ensuring that the licensed services operating in this spectrumwill continue to operate seamlessly. Accordingly, some systems may allowfor licensed operators to determine if their radio links are beingaffected by interference and may generate reports to inform regulatoryauthorities.

Interference may be present at different severity levels. In someembodiments, including:

-   -   1. Link-disrupting interference—when the radio link is lost.    -   2. Error-generating interference—when the radio link is taking        errors.    -   3. Performance-affecting interference—when the radio link is        stressed due to interference, causing modulation changes, power        adjustments and/or link availability reduction, but below the        point of causing errors. This type of interference usually goes        unnoticed.    -   4. Negligible or no interference.

Each of the different severity levels may have different impacts on thecommunication path. Note the example impacts below.

-   -   1. Link-disrupting interference—When the radio link is lost,        regardless of cause, all traffic on the radio link must be        rerouted over a different path or over a different media. If        such options are unavailable, the area served by the radio link        will have a communications outage (loss of service) while the        radio link is down. Re-routing traffic may cause congestion in        other parts of the network, longer latency, higher packet delay        variation and/or potential loss of traffic especially in lower        priority services. A communications outage, depending on the        type of network, can cause revenue loss, loss of mission        critical services, energy grid blackouts, synchronization loss,        etc.    -   2. Error-generating interference—Radio link errors may cause        packet re-transmission for some services and, depending on the        severity, can cause congestion and inherently additional packet        loss. Retransmissions may lead to latency and packet delay        variation problems.    -   3. Performance-affecting interference—When the radio link has        degraded but not to a level sufficient to cause errors, the        following effects may be noticed based on the circumstances:        -   a. If the radio link has ATPC and ACM enabled, these            features may compensate for the degradation. ATPC increases            the output power in the far end transmitter to try to bring            the SNR to the expected nominal value. Operating at a higher            output power may cause additional interference in the            surrounding area. If a higher output power is maintained            over a long period of time, the higher power can reduce            product life. ACM downshifts coding and/or modulation to            compensate for the degradation. Downshifting causes a            reduction in link capacity and may cause congestion leading            to higher latency and packet delay variation in some            services and potential traffic loss in others.        -   b. When the radio link has degraded but insufficiently to            trigger a compensation action and/or the compensation            mechanisms are not enabled, the interference may reduce the            fade margin of the radio link and may cause the radio link            to have lower availability. Thus, the radio link may be more            susceptible to fail when other conditions arise, because the            radio link will have insufficient means to compensate for            the added impairments. When this happens, the link may be            pushed prematurely into cases 1 and 2 above.

When interference is degrading a radio link, systems may respond byperforming any or all of the following:

-   -   1. Document the event with all the pertinent information that        led to the interference detection.    -   2. Based on the severity level, corrective actions may include        any combination of:        -   a. Increase the output power or turn on ATPC for automatic            operation.        -   b. Operate in a more robust code modulation or turn on ACM            for automatic operation.        -   c. Move to a larger antenna size.        -   d. Use a diversity partner.        -   e. Adjust receiver equalizer coefficients to improve the            quality of the received signal.        -   f. Operate the link in a different polarization.        -   g. Convert the link from non-space diversity to space            diversity.        -   h. Migrate the radio link to a different frequency channel.    -   3. Raise an alarm and seek support to resolve the issue.

Some responses may be available only if the system is configured toexecute them, e.g., if the link has Adaptive Code Modulation (ACM)enabled, if the link has Automatic Transmit Power Control (ATPC)enabled, and/or the like.

In some embodiments, systems may use parameters present in the radiomodem and/or in the radio frequency unit (RFU) to determine when anexternal interferer is or may be present in the path. Systems may alsouse these parameters to validate the interference and/or discriminateamong the different interference types.

In some embodiments, systems may determine that interference isaffecting the radio link regardless of the source type causing it andregardless of whether the interfering signal is steady or bursty,regular or irregular, and/or caused by a time-division duplexing (TDD)or frequency-division duplexing (FDD) signal. Systems may discriminatebetween multipath conditions (and other electromagnetic propagationconditions) and external interference and may filter out false positiveinterference detections.

In some embodiments, systems may record the interference conditions wheninterference is detected in a historical database. Systems may use thehistorical database to augment link-performance-over-time reports and asa reference for future events. Systems can use the historical databaseto assist in detecting interference and to assist in evaluating eventsby creating a link operation baseline. In some embodiments, radio linkbaselining may be performed in a period when no interference is observedand when the radio link is not being subjected to fading and/ormultipath conditions. Baselining may serve as a reference in theinterference analysis and may be a fundamental element to determine thethresholds applied.

In some embodiments, systems may differentiate between situations wherethe radio signal is degraded by interferer signals and degradationcaused by naturally occurring phenomena, equipment malfunction,installation problems, etc. Some causes of signal degradation can beaddressed in a procedural way. For example, during the initial linksetup, it is expected that the installation team will confirm that theradio equipment is operating within expected performance parametersdesignated for the radio link and will perform and record a number oftests that can be used as documented proof that the installation wasperformed correctly. This may include monitoring for the presence ofunwanted radio signals in the channel that will be occupied by thecarrier being setup and also in the adjacent channels. The reportsgenerated during installation may also be used in operation baseliningand/or in showing how the radio link was operating immediately afterinstallation.

As noted above, radio link performance degradation may be caused bynaturally occurring phenomena, like rain. Rain causes a weaker signal tobe received by the receiver on the other end of the radio link due tothe higher level of radiated signal absorption of water compared to air.This reduction in signal strength is normally referred to as radio linkfading. In the case of radio link fading, the signal present at thereceiver antenna port has been reduced by the attenuating effects of thefading condition. Systems may try to compensate for radio linkperformance degradation by, for example, (1) using gain control stagesin the receiver chain, (2) switching to a stronger modulation/codingscheme (if ACM is enabled), and/or (3) causing the far end transmitterto increase its output power (if ATPC is enabled). In some cases, thefading condition can be so severe that it leads to errors in the radiolink or losing the entire radio link all together.

In some embodiments, systems may look at radio parameters to assist indifferentiating between external interference and other conditionscausing link degradation. Under normal circumstances, when externalinterference is present, the Received Signal Level (RSL) may remainstrong while other link performance parameters show signal degradationeffects. In the other link degradation situations, the Received SignalLevel (RSL) often degrades along with the other link performanceparameters.

Focusing on external interference, systems may review radio parameterspresent in the radio modem and in the radio frequency unit to determinewhen an external interferer is or may be present in the path. In someembodiments, systems may evaluate the Received Signal Level (RSL), theSignal-to-Noise Ratio (SNR), the Demodulator-Not-Locked alarm (DNL), theErrored Seconds (ES) and Severely Errored Seconds (SES) performanceindicators, the Uncoded Bit Error Rate (U-BER), the Adaptive Coding andModulation (ACM) indicators, Automatic Power Control (ATPC) adjustments,fade margin reduction, and/or Equalizer Coefficients. In someembodiments, systems may use one, some or all of these parameters toassist in determining whether one or more external interferers arepresent and affecting the radio link and/or to determine the severitylevel and the conditions that they produce.

The main overall considerations for interference detection involveprimarily a good Received Signal Level (RSL) and a bad Signal to NoiseRatio (SNR). However, there are a number of conditions where the SNR maynot be bad enough to create evident effects (like errors, alarms,Demodulator Not Locked (DNL)), but still degrade the radio link enoughto cause reductions in capacity due to a downshift in modulation/coding(e.g., ACM) and/or increase in the far end output power to compensatefor the SNR reduction (e.g., ATPC). Even further, the radio link may beoperating with a reduced fade margin that may cause a lower linkavailability and therefore may be more susceptible to link failure.

Embodiments of the present invention provide an interference detectionsystem in a point-to-point radio system, the point-to-point radio systemincluding a first site in radio communication with a second site,comprising at least one processor; and memory storing computerinstructions, the computer instructions when executed by the at leastone processor causing the system to perform, gathering a temporalsnapshot of radio parameter values associated with at least a first siteof a point-to-point radio system, the radio parameter values includingat least a receive signal level (RSL) value and at least one other radioparameter value correlated with signal degradation during the temporalsnapshot; determining whether the RSL value is greater than an RSLthreshold; determining whether the other radio parameter value indicatesa threshold level of signal degradation during the temporal snapshot; atleast when the RSL is greater than the RSL threshold and the otherparameter indicates a threshold level of signal degradation during thetemporal snapshot, then determining that external interference is likelypresent during the temporal snapshot; at least when the RSL is notgreater than the RSL threshold, then determining that the externalinterference is likely not present during the temporal snapshot; andperforming a responsive action to a determination of the externalinterference being likely present during the temporal snapshot.

The radio parameter values may include radio parameter values associatedwith a modem and a radio frequency unit at the first site during thetemporal snapshot. The other radio parameter value may include aDemodulator Not Locked (DNL) Alarm, and the other radio parameter valuemay indicate a threshold level of signal degradation at least when theDNL Alarm is active. The other radio parameter value may include ErroredSeconds (ES) or Severely Errored Seconds (SES) value, and the otherradio parameter value may indicate a threshold level of signaldegradation at least when the ES or SES value is increasing from aprevious sample. The other radio parameter value may include asignal-to-noise ratio (SNR) value, and the other radio parameter valuemay indicate a threshold level of signal degradation at least when atleast the SNR value is less than a threshold. The other radio parametervalue may include a change in an Uncoded Bit Error Rate (U-BER), and theother radio parameter value may indicate a threshold level of signaldegradation at least when the change in the U-BER is greater than athreshold. The other radio parameter may include Adaptive CodeModulation (ACM) data, and the other radio parameter value may indicatea threshold level of signal degradation at least when ACM is active andnegative. The other radio parameter value may include Automatic TransmitPower Control (ATPC) data, and the other radio parameter value mayindicate a threshold level of signal degradation at least when ATPC isenabled and a power adjustment is greater than a threshold.

The computer instructions when executed by the processor may furthercause the system to perform evaluating interference persistence; anddetermining a false positive at least when the interference persistenceis less than a minimum threshold duration.

The computer instructions when executed by the processor may furthercause the system to perform determining an amount of interferencevariation; identifying the external interference as a steady interfererat least when the amount of interference variation is less than athreshold; and identifying the external interference as a continuousbursty interferer at least when the amount of interference variation isgreater than the threshold.

The computer instructions when executed by the processor may furthercause the system to perform determining first interference effects on afirst receiver at the first site in space diversity with a secondreceiver at the first site; determining second interference effects onthe second receiver at the first site; comparing the first interferenceeffects with the second interference effects; and at least when thefirst interference effects are substantially the same as the secondinterference effects, then validating the external interference.

The computer instructions when executed by the processor may furthercause the system to perform determining first SNR on a first receiver atthe first site in space diversity with a second receiver at the firstsite; determining second SNR on the second receiver; at least when thefirst SNR indicates signal degradation while the second SNR does notindicate signal degradation and when thereafter the first SNR improvesor clears while the second SNR deteriorates, then identifying theexternal interference as a likely multipath interference.

The computer instructions when executed by the processor may furthercause the system to perform comparing a near-end interference conditionwith a far-end interference condition; and at least when the near-endinterference condition is not substantially similar to the far-endinterference condition, the validating the external interference.

The computer instructions when executed by the processor may furthercause the system to perform searching a historical database for recordsindicative of an interference pattern or correlation with externalevents; and using the interference pattern or correlation with externalevents to assist in identifying future interferences as not being due toan external interferer.

The computer instructions when executed by the processor may furthercause the system to perform gathering a bin of radio parameterinformation, the bin of radio parameter information including maximumand minimum levels of RSL values and at least one other radio parametervalues occurring during a specific time period; and evaluating the binof radio parameter information to determine a likelihood of the externalinterference occurring in any temporal snapshot within the specific timeperiod, before performing an analysis of any temporal snapshot of radioparameter values within the specific time period. The specific timeperiod may include a 15-minute time period.

Embodiments of the present invention may provide an interferencedetection method in a point-to-point radio system, the point-to-pointradio system including a first site in radio communication with a secondsite, comprising: gathering a temporal snapshot of radio parametervalues associated with at least a first site of a point-to-point radiosystem, the radio parameter values including at least a receive signallevel (RSL) value and at least one other radio parameter valuecorrelated with signal degradation during the temporal snapshot;determining whether the RSL value is greater than an RSL threshold;determining whether the other radio parameter value indicates athreshold level of signal degradation during the temporal snapshot; atleast when the RSL is greater than the RSL threshold and the otherparameter indicates a threshold level of signal degradation during thetemporal snapshot, then determining that external interference is likelypresent during the temporal snapshot; at least when the RSL is notgreater than the RSL threshold, then determining that the externalinterference is likely not present during the temporal snapshot; andperforming a responsive action to a determination of the externalinterference being likely present during the temporal snapshot.

The interference detection method may further comprise evaluatinginterference persistence; and determining a false positive at least whenthe interference persistence is less than a minimum threshold duration.

The interference detection method may further comprise determining anamount of interference variation; identifying the external interferenceas a steady interferer at least when the amount of interferencevariation is less than a threshold; and identifying the externalinterference as a continuous bursty interferer at least when the amountof interference variation is greater than the threshold.

The interference detection method may further comprise determining firstinterference effects on a first receiver at the first site in spacediversity with a second receiver at the first site; determining secondinterference effects on the second receiver at the first site; comparingthe first interference effects with the second interference effects; andat least when the first interference effects are substantially the sameas the second interference effects, then validating the externalinterference.

The interference detection method may further comprise determining firstSNR on a first receiver at the first site in space diversity with asecond receiver at the first site; determining second SNR on the secondreceiver; and at least when the first SNR indicates signal degradationwhile the second SNR does not indicate signal degradation and whenthereafter the first SNR improves or clears while the second SNRdeteriorates, then identifying the external interference as a likelymultipath interference.

The interference detection method may further comprise comparing anear-end interference condition with a far-end interference condition;and at least when the near-end interference condition is notsubstantially similar to the far-end interference condition, thevalidating the external interference.

The interference detection method may further comprise searching ahistorical database for records indicative of an interference pattern orcorrelation with external events; and using the interference pattern orcorrelation with external events to assist in identifying futureinterferences as not being due to an external interferer.

The interference detection method may further comprise gathering a binof radio parameter information, the bin of radio parameter informationincluding maximum and minimum levels of RSL values and at least oneother radio parameter values occurring during a specific time period;and evaluating the bin of radio parameter information to determine alikelihood of the external interference occurring in any temporalsnapshot within the specific time period, before performing an analysisof any temporal snapshot of radio parameter values within the specifictime period.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a point-to-point radio system, in accordance withsome embodiments of the present invention.

FIG. 2 is a diagram illustrating details of the interference detectionsystem of FIG. 1, in accordance with some embodiments of the presentinvention.

FIG. 3A is a diagram illustrating details of a site of FIG. 1, inaccordance with some embodiments of the present invention.

FIG. 3B is a diagram illustrating details of a site of FIG. 1, inaccordance with some embodiments of the present invention.

FIG. 4 shows a graphical representation of a point-to-point radio systemimplementing space diversity and having multipath effects.

FIG. 5 is a flowchart illustrating a main method of evaluatinginterference in the point-to-point radio system of FIG. 1, in accordancewith some embodiments of the present invention.

FIG. 6 is a flowchart illustrating a method of validating aninterference detection based on persistence, in accordance with someembodiments of the present invention.

FIG. 7 is a flowchart illustrating a method of validating aninterference detection based on multipath effects, in accordance withsome embodiments of the present invention.

FIG. 8 is a flowchart illustrating a method of validating aninterference detection based on symmetry, in accordance with someembodiments of the present invention.

FIG. 9 is a flowchart illustrating a method of validating aninterference detection based on patterns, in accordance with someembodiments of the present invention.

FIG. 10 is a flowchart illustrating a method of using condensedinformation to trigger the interference detection method, in accordancewith some embodiments of the present invention.

FIG. 11 is a block diagram illustrating details of a computer system.

DETAILED DESCRIPTION

The following description is provided to enable a person skilled in theart to make and use various embodiments of the invention. Modificationsare possible. The generic principles defined herein may be applied tothe described and other embodiments without departing from the spiritand scope of the invention. Thus, the claims are not intended to belimited to the embodiments disclosed, but are to be accorded the widestscope consistent with the principles, features and teachings herein.

Some embodiments of the invention perform in-line interferencemonitoring in point-to-point (PTP) radio links. Being able to accuratelydetermine if interference is affecting a PTP radio link is important toidentify problems and improve performance. Some embodiments may operatewhile the PTP radio link is online and without having to stop ongoingpayload transport.

Some embodiments may apply to any of the microwave frequencies availablefor wireless data transport in the United States and internationally.Some systems may be particularly useful for licensed users of the 6 GHzfrequency band in the United States where the Federal CommunicationsCommission (FCC) has decided to allow unlicensed use of the band foroperations relying on WiFi and other technical standards. The FCCproposes to allow unlicensed use in the 5.925-7.125 GHz (6 GHz) bandwhile ensuring that the licensed services operating in this spectrumwill continue to operate seamlessly. Accordingly, some systems may allowfor licensed operators to determine if their radio links are beingaffected by interference and may generate reports to inform regulatoryauthorities.

Interference may be present at different severity levels. In someembodiments, including:

-   -   1. Link-disrupting interference—when the radio link is lost.    -   2. Error-generating interference—when the radio link is taking        errors.    -   3. Performance-affecting interference—when the radio link is        stressed due to interference, causing modulation changes, power        adjustments and/or link availability reduction, but below the        point of causing errors. This type of interference usually goes        unnoticed.    -   4. Negligible or no interference.

Each of the different severity levels may have different impacts on thecommunication path. Note the example impacts below.

-   -   4. Link-disrupting interference—When the radio link is lost,        regardless of cause, all traffic on the radio link must be        rerouted over a different path or over a different media. If        such options are unavailable, the area served by the radio link        will have a communications outage (loss of service) while the        radio link is down. Re-routing traffic may cause congestion in        other parts of the network, longer latency, higher packet delay        variation and/or potential loss of traffic especially in lower        priority services. A communications outage, depending on the        type of network, can cause revenue loss, loss of mission        critical services, energy grid blackouts, synchronization loss,        etc.    -   5. Error-generating interference—Radio link errors may cause        packet re-transmission for some services and, depending on the        severity, can cause congestion and inherently additional packet        loss. Retransmissions may lead to latency and packet delay        variation problems.    -   6. Performance-affecting interference—When the radio link has        degraded but not to a level sufficient to cause errors, the        following effects may be noticed based on the circumstances:        -   a. If the radio link has ATPC and ACM enabled, these            features may compensate for the degradation. ATPC increases            the output power in the far end transmitter to try to bring            the SNR to the expected nominal value. Operating at a higher            output power may cause additional interference in the            surrounding area. If a higher output power is maintained            over a long period of time, the higher power can reduce            product life. ACM downshifts coding and/or modulation to            compensate for the degradation. Downshifting causes a            reduction in link capacity and may cause congestion leading            to higher latency and packet delay variation in some            services and potential traffic loss in others.        -   b. When the radio link has degraded but insufficiently to            trigger a compensation action and/or the compensation            mechanisms are not enabled, the interference may reduce the            fade margin of the radio link and may cause the radio link            to have lower availability. Thus, the radio link may be more            susceptible to fail when other conditions arise, because the            radio link will have insufficient means to compensate for            the added impairments. When this happens, the link may be            pushed prematurely into cases 1 and 2 above.

When interference is degrading a radio link, systems may respond byperforming any or all of the following:

-   -   4. Document the event with all the pertinent information that        led to the interference detection.    -   5. Based on the severity level, corrective actions may include        any combination of:        -   a. Increase the output power or turn on ATPC for automatic            operation.        -   b. Operate in a more robust code modulation or turn on ACM            for automatic operation.        -   c. Move to a larger antenna size.        -   d. Use a diversity partner.        -   e. Adjust receiver equalizer coefficients to improve the            quality of the received signal.        -   f. Operate the link in a different polarization.        -   g. Convert the link from non-space diversity to space            diversity.        -   h. Migrate the radio link to a different frequency channel.    -   6. Raise an alarm and seek support to resolve the issue.

Some responses may be available only if the system is configured toexecute them, e.g., if the link has Adaptive Code Modulation (ACM)enabled, if the link has Automatic Transmit Power Control (ATPC)enabled, and/or the like.

In some embodiments, systems may use parameters present in the radiomodem and/or in the radio frequency unit (RFU) to determine when anexternal interferer is or may be present in the path. Systems may alsouse these parameters to validate the interference and/or discriminateamong the different interference types.

In some embodiments, systems may determine that interference isaffecting the radio link regardless of the source type causing it andregardless of whether the interfering signal is steady or bursty,regular or irregular, and/or caused by a time-division duplexing (TDD)or frequency-division duplexing (FDD) signal. Systems may discriminatebetween multipath conditions (and other electromagnetic propagationconditions) and external interference and may filter out false positiveinterference detections.

In some embodiments, systems may record the interference conditions wheninterference is detected in a historical database. Systems may use thehistorical database to augment link-performance-over-time reports and asa reference for future events. Systems can use the historical databaseto assist in detecting interference and to assist in evaluating eventsby creating a link operation baseline. In some embodiments, radio linkbaselining may be performed in a period when no interference is observedand when the radio link is not being subjected to fading and/ormultipath conditions. Baselining may serve as a reference in theinterference analysis and may be a fundamental element to determine thethresholds applied.

In some embodiments, systems may differentiate between situations wherethe radio signal is degraded by interferer signals and degradationcaused by naturally occurring phenomena, equipment malfunction,installation problems, etc. Some causes of signal degradation can beaddressed in a procedural way. For example, during the initial linksetup, it is expected that the installation team will confirm that theradio equipment is operating within expected performance parametersdesignated for the radio link and will perform and record a number oftests that can be used as documented proof that the installation wasperformed correctly. This may include monitoring for the presence ofunwanted radio signals in the channel that will be occupied by thecarrier being setup and also in the adjacent channels. The reportsgenerated during installation may also be used in operation baseliningand/or in showing how the radio link was operating immediately afterinstallation.

As noted above, radio link performance degradation may be caused bynaturally occurring phenomena, like rain. Rain causes a weaker signal tobe received by the receiver on the other end of the radio link due tothe higher level of radiated signal absorption of water compared to air.This reduction in signal strength is normally referred to as radio linkfading. In the case of radio link fading, the signal present at thereceiver antenna port has been reduced by the attenuating effects of thefading condition. Systems may try to compensate for radio linkperformance degradation by, for example, (1) using gain control stagesin the receiver chain, (2) switching to a stronger modulation/codingscheme (if ACM is enabled), and/or (3) causing the far end transmitterto increase its output power (if ATPC is enabled). In some cases, thefading condition can be so severe that it leads to errors in the radiolink or losing the entire radio link all together.

In some embodiments, systems may look at radio parameters to assist indifferentiating between external interference and other conditionscausing link degradation. Under normal circumstances, when externalinterference is present, the Received Signal Level (RSL) may remainstrong while other link performance parameters show signal degradationeffects. In the other link degradation situations, the Received SignalLevel (RSL) often degrades along with the other link performanceparameters.

Focusing on external interference, systems may review radio parameterspresent in the radio modem and in the radio frequency unit to determinewhen an external interferer is or may be present in the path. In someembodiments, systems may evaluate the Received Signal Level (RSL), theSignal-to-Noise Ratio (SNR), the Demodulator-Not-Locked alarm (DNL), theErrored Seconds (ES) and Severely Errored Seconds (SES) performanceindicators, the Uncoded Bit Error Rate (U-BER), the Adaptive Coding andModulation (ACM) indicators, Automatic Power Control (ATPC) adjustments,fade margin reduction, and/or Equalizer Coefficients. In someembodiments, systems may use one, some or all of these parameters toassist in determining whether one or more external interferers arepresent and affecting the radio link and/or to determine the severitylevel and the conditions that they produce.

In the table below, principles for external interferer detection and theeffects that they may cause are shown. As noted, the main overallconsiderations for interference detection involve primarily a goodReceived Signal Level (RSL) and a bad Signal to Noise Ratio (SNR).However, there are a number of conditions where the SNR may not be badenough to create evident effects (like errors, alarms, Demodulator NotLocked (DNL)), but still degrade the radio link enough to causereductions in capacity due to a downshift in modulation/coding (e.g.,ACM) and/or increase in the far end output power to compensate for theSNR reduction (e.g., ATPC). Even further, the radio link may beoperating with a reduced fade margin that may cause a lower linkavailability and therefore may be more susceptible to link failure.

Alarm/ SNR Failure ATPC/ACM RSL Interference Low DNL Both if enabledGood Yes Low Errored Both if enabled Good Yes Seconds Moderately NonePower raised FE Good Maybe/Likely Low Modulation drop NE Slightly LowNone No Change or not Good Maybe enabled. Use U-BER

FIG. 1 is a diagram of a point-to-point (PTP) radio system 100, inaccordance with some embodiments of the present invention. The PTP radiosystem 100 includes a first site (site A) 102 in radio communication(e.g., microwave and/or millimeter wave communication) with a secondsite (site B) 104. Each of the first site 102 and the second site 104are coupled via a computer network 128 (e.g., wired and/or wireless) toa server 106 (which may be located at or part of a network operationscenter (NOC)).

The first site 102 includes a first receiver (receiver A) 108, a firstagent (agent A) 110, a first transmitter (transmitter A) 112, and afirst antenna 114. The first receiver 108 includes circuitry to receivesignals via the first antenna 114 from the second site 104. The firsttransmitter 112 includes circuitry to transmit signals to the firstantenna 114 for delivery to the second site 104. Although shown assingular, the first site 102 may have any number of first receivers 108,any number of first transmitters 112, and any numbers of first antennas114. The first agent 110 operates to gather parameters associated withthe first receiver 108 and/or the first transmitter 112 (and/or possiblyfrom the second receiver 116 and/or the second transmitter 120), whichit may provide to the NMS 124 for system monitoring. The first agent 110may also operate to receive configuration information and/orinstructions to configure the first site 102 (e.g., the first receiver108 and/or the first transmitter 112) based on interferences detected.

The second site 104 includes a second receiver (receiver B) 116, asecond agent (agent A) 118, a second transmitter (transmitter A) 120,and a second antenna 122. The second receiver 116 includes circuitry toreceive signals via the second antenna 122 from the first site 102. Thesecond transmitter 120 includes circuitry to transmit signals to thesecond antenna 122 for delivery to the first site 102. Although shown assingular, the second site 104 may have any number of second receivers116, any number of second transmitters 120, and any numbers of secondantennas 122. The second agent 118 operates to gather parametersassociated with the second receiver 116 and/or the second transmitter120 (and/or possibly the first receiver 108 and/or the first transmitter112), which it may provide to the NMS 124 for system monitoring. Thesecond agent 118 may also operate to receive configuration informationand/or instructions to configure the second site 104 (e.g., the secondreceiver 116 and/or the second transmitter 120) based on interferencesdetected.

The server 106 includes a network management/monitoring system (NMS) orSoftware-Defined Networking (SDN) controller 124, referred to herein asNMS 124. The server 106 further includes an interference detectionsystem 126. The NMS 124 may include hardware, software and/or firmwareconfigured to evaluate parameters received from network agents, e.g.,from the first agent 110 and/or the second agent 118. The interferencedetection system 126 may include hardware, software and/or firmwareconfigured to evaluate parameters from the NMS 126 to identify externalinterference, determine the severity level of the interference,validate/classify the interference, identify false positives, and/or thelike. Although shown as located on the server 106, the interferencedetection system 126 can be located anywhere in the network, includingat a site or distributed among several sites.

FIG. 2 is a diagram illustrating details of the interference detectionsystem 126, in accordance with some embodiments of the presentinvention. The interference detection system 126 includes a datacollecting engine 202, an interference detector 204, avalidation/classification engine 206, a data storage engine 208, ahistorical database 210, a condensed evaluation engine 212, and aresponse engine 214.

In some embodiments, the data collecting engine 202 includes hardware,software and/or firmware configured to gather radio parameters presentin the radio modem and/or in the radio frequency unit (RFU). In someembodiments, the data collecting engine 202 gathers the radio parametersfrom the NMS 124. In some embodiments, the data collecting engine 202may gather the radio parameters by communicating directly with theagents at the various sites, e.g., with the first agent 110 and thesecond agent 118. The data collecting engine 202 may cooperate with thedata storage engine 208 to store the radio parameters in the historicaldatabase 210.

In some embodiments, the data collecting engine 202 may gather radioparameters corresponding to “temporal snapshots”. That is, the datacollecting engine 202 may gather the radio parameters of tight windowsof time, to ensure that the radio parameters correlate with each otherand correlate in time to interference that may be caused by an externalinterferer (e.g., ±5 msec tolerance).

In some embodiments, the interference detector 204 includes hardware,software and/or firmware configured to evaluate the radio parameters toassist in identifying potential external interference, as opposed to theother conditions that may cause link degradation. The interferencedetector 204 may look at whether the Received Signal Level (RSL) remainsstrong while other link performance parameters show degradation effects(suggestive of an external interference), or whether the RSL degradedalong with the other link performance parameters (suggestive of anon-interference type degradation).

The interference detector 204 may evaluate the Received Signal Level(RSL), the Signal-to-Noise Ratio (SNR), the Demodulator-Not-Locked alarm(DNL), the Errored Seconds (ES) and Severely Errored Seconds (SES)performance indicators, the Uncoded Bit Error Rate (Uncoded BER), theAdaptive Coding and Modulation indicators, Automatic Power Control(ATPC) adjustments, fade margin reduction, and/or EqualizerCoefficients. In some embodiments, the interference detector 204 may useone, some or all of these parameters to assist in determining whetherone or more interferers are present and affecting the radio link.

The interference detector 204 may evaluate data generated duringinstallation to support operation baselining, thereby supporting thegeneration of the various thresholds used herein and described in moredetail below.

The validation/classification engine 206 includes hardware, softwareand/or firmware configured to validate external interferer signal basedon validation criteria, including persistence, multipath effects,symmetry, and historical records. The different validation methods aredescribed in detail with reference to FIGS. 6-9.

The data storage engine 208 includes hardware, software and/or firmwareconfigured to record in the historical database 210 the radio parametersand interference conditions when interference is detected. Theinterference detector 204, validation/classification engine 206 and/orcondensed evaluation engine 212 may use the historical database 210 toassist in detecting interference and to assist in creating a linkoperation baseline. In some embodiments, baselining of the radio linkmay be performed in a period when no interference is observed and whenthe radio link is not being subjected to fading and/or multipathconditions, as operation baselining may serve as a reference in theinterference analysis and may be a fundamental element to determine thethresholds applied in it. Further, the interference detection system 126may be configured to augment link-performance-over-time reports and as areference for future events.

The condensed evaluation engine 212 includes hardware, software and/orfirmware configured to evaluate aggregated bins of radio parametersassociated with a longer time period to assist in identifying apossibility of external interference in that time period, meriting amore detailed evaluation of the radio parameters associated with thetemporal snapshots within the time period or a more detailed evaluationof the radio parameters associated with a real-time temporal snapshot.

The response engine 214 includes hardware, software and/or firmwareconfigured to respond to the presence of interference. Some responsesmay involve generating and transmitting reports, setting off alarms,informing regulatory entities, modifying configurations, etc.

FIG. 3A is a diagram illustrating details of a site 300, in accordancewith some embodiments of the present invention. Site 300 may illustrateexample details of the first site 102 and/or the second site 104.

Site 300 includes an outdoor unit (ODU) 302 coupled to the antenna 330and over a communication link (e.g., coaxial cable) 328 to an indoorunit (IDU) 304, which is coupled to a mediator 306. Although shown as asplit-mount architecture, embodiments are not limited to split-mountsystems. Embodiments will work with all-indoor and/or all-outdoorsystems. The ODU 302 includes a transmitter unit 308, a receiver unit310 and a controller 312, each coupled to an ODU interface 314. The IDU304 includes a modem 318 and a controller 320, each coupled to an IDUinterface 316, which is coupled to the ODU interface 314. The IDU 304further includes a communication engine 322 coupled to the controller320 and coupled via the computer network 128 to the NMS 124. Themediator 306 includes a controller/agent 326 coupled to a communicationengine 326, which is coupled to the communication engine 322 of the IDU304.

In operation, payload is delivered to and from customer premiseequipment (not shown). The modem 318 receives and modulates the outgoingpayload and forwards it onto the communication link 328 to the ODU 302.The transmitter unit 308 in the ODU 302 forwards the outgoing payload tothe antenna 330 for radio transport to the second site. Further, theantenna 330 receives incoming payload and forwards it to the receiverunit 310, which forwards it to the modem 318, which demodulates theincoming payload and forwards it to the customer premise equipment.

The controller 312, controller 320 and controller/agent 326 operate togather radio parameters associated with the various components,including the modem 318, the transmitter unit 308 and the receiver unit310. Further, the controller 312, controller 320 and controller/agent326 operate to control the configuration settings of the components ofthe ODU 302 and IDU 304 (e.g., ACM, ATPC, etc.).

The communication engine 322 operates to transmit radio parameters tothe NMS 124 and/or interference detection system 126.

In some embodiments, the mediator 306 may be a separate computing devicethat communicatively couples to the IDU 304 via the communication engine322. Further, the controller/agent 326 may operate to assist ingathering and transmitting the radio parameters needed by theinterference detection system 126 and to assist in managing anyresponsive actions by the site 300 to support management ofinterferences detected by the interference detection system 126.

FIG. 3B is a diagram illustrating details of a site 350, in accordancewith some embodiments of the present invention. The elements of site 350may be similar to the site 300, except that the functions of themediator 306, the controller/agent 326, and the communication engines322 and 324 may be wrapped into an agent 352 located in the IDU 304 inplace of the controller 320.

FIG. 4 shows a graphical representation of PTP radio system 400 withmultipath interference in a space diversity link, which may be aparticular case of the PTP radio system 100. As shown, the PTP radiosystem 400 includes a first site 102 in communication over a radiochannel with a second site 104. The first site 102 includes a firstantenna system 402 (with a first transmitter and a first receiver, notshown) and a second antenna system 404 (with a second transmitter and asecond receiver, not shown). The second site 104 includes a thirdantenna system 406 (with a third transmitter and a third receiver, notshown) and a fourth antenna system 408 (with a fourth transmitter and afourth receiver, not shown). The first antenna system 402 at the firstsite 102 transmits a radio signal, which is being reflected off areflection layer 410 and which is being received with multipath effectsby each of the third antenna system 406 and the fourth antenna system408.

As can be seen, the effects of multipath interference act similarly tothat of an external interferer. However, the actions to be taken arelikely considerably different. For this reason, in some embodiments,identifying interference events due to multipath effects may be acritical part of the interference detection algorithms. In someembodiments, multipath propagation may be particularly relevant inmicrowave frequencies below 13 GHz, where the multipath propagationphenomenon is more common.

Multipath interference is typically caused by the reflection of anoriginally transmitted signal off an elevated refractive layer(inversion layer), a water body and/or other terrestrial object such asmountains or buildings. Multipath interference can also be caused byatmospheric ducting and ionospheric reflection and refraction. Since thereflected signal arrives at a later time and out of phase with theoriginally transmitted signal (e.g., due to path distance), thereflected signal acts as an interferer and can have severe effects onthe radio link.

In a space diversity context, as shown in FIG. 4, multipath interferencemay affect both the third and fourth receivers of the third and fourthantenna systems 406 and 408 in different ways and at different times,e.g., affecting the third receiver of the third antenna system 406 at afirst time and the fourth receiver of the fourth antenna system 408 atas second later time. In the case of non-space diversity links, thedetection of multipath interference may be more complicated and mayrequire the validation/classification engine 206 to evaluate modemparameters, e.g., the receiver equalizer coefficients. Thevalidation/classification engine 206 may also use the historicaldatabase 210 associated with the radio link to determine if aninterference event is happening at regular intervals and/or whether thisinterference event is correlated to some specific naturally occurringphenomenon like tides, weather patterns, sunrise/sunset, etc. One of thecharacteristics of multipath interference is that it often has dailyand/or seasonal patterns. The validation/classification engine 206 canuse this information to assist in identifying a multipath type ofinterference.

FIG. 5 is a flowchart illustrating a main method 500 of evaluatinginterference in the PTP system 100, in accordance with some embodimentsof the present invention. In some embodiments, the main method 500 maybe responsible for determining whether the microwave radio link is beingaffected by interference at any given point in time. The main method 500may also be responsible for discriminating interference from fading andfor initiating additional methods to conduct classification of theinterference into different potential interference types.

In some embodiments, for the main method 500 to work correctly, in step502, data is evaluated as a temporal snapshot. That is, all of theparameters that the interference detection system 126 uses to determinewhether an interferer is present preferably have been captured at thesame time (e.g., ±5 msec tolerance). This supports appropriate datacorrelation in the parameters representing the condition being evaluatedat the particular instance of time.

As indicated herein, the interference detector 204 may determine thepresence of interference when it identifies strong RSL present and theperformance of the radio link shows signs of deterioration. In step 504,the data collecting engine 202 reads RSL, SNR, DNL, ES, SES, RBER, FEPower Level, Mod Change, and/or the like, for the given temporalsnapshot. In step 506, the interference detector 204 determines, fromthe radio parameters collected, whether the RSL is strong enough. Thismay be established according to an RSL threshold based on the specificlink conditions (link budget and baseline link performance, amongothers). In other words, the RSL threshold RSL_Th may be generated basedon the expected RSL for that specific radio link, since many of the linkcharacteristics vary from link to link, like the radio link separation(link distance), the type of antennas used, output power and other linkparameters. Those will ultimately determine the expected RSL.

If in step 506 the interference detector 204 determines that the RSL isbelow the RSL threshold, the interference detector 204 in step 508 willconsider the radio link to be under fading activity. In this situation,the interference detector 204 will verify if the fading is deep enoughto affect the corresponding SNR or not. This information may be recordedby the data storage engine 208 in the historical database 210 as part ofthe historical record of the radio link. The interference detector 204may not pursue the information further in the interferencedetermination. The main method 500 will return to step 502 to evaluatethe radio parameters from the next temporal snapshot.

If in step 506 the interference detector 204 determines that the RSL isequal or above the RSL threshold, then the interference detector 204 maydetermine that the first component of the interference detection (astrong RSL) has been met. In some embodiments, the interference detector204 proceeds to determine if the radio link has deteriorated. Theinterference detector 204 may evaluate the different conditions thatindicate link degradation in order of severity.

When the radio link has been lost due to interference, the DNL alarmwould have been raised and the SNR would have dropped to 0.0. Since theDNL alarm may take slightly longer to raise due to external processing,the SNR turning to zero could be used instead. This type of interferenceis explicit and noticeable. Accordingly, in step 510, the interferencedetector 204 determines whether the DNL alarm is active. If so, then theinterference detector 204 in step 512 determines that an externalinterferer is very likely, and proceeds to run validation algorithms.

When the radio link is taking errors due to interference, theinterference detector 204 in step 514 can determine if the ES and SESindicators are increasing from the previous sample to the currentsample, which will indicate that, in the time interval, there wereerrors detected. This type of interference is explicit and noticeable.If so, the interference detector 204 in step 516 determines that anexternal interferer is very likely, and proceeds to run validationalgorithms.

Performance-affecting interference type A—When the radio link hasdegraded due to the interference but below the severity level ofgenerating errors, and when the radio link configuration hascompensation mechanisms enabled, the PTP system 100 may be trying tocompensate for the degradation. In some embodiments, such compensationmay only be possible if the radio link configuration has such mechanismsenabled. ACM and ATPC are the two most common mechanisms used tocompensate for degradation. ATPC increases output power in the far endtransmitter (e.g., the first transmitter 112) to try to bring the SNR tothe expected nominal value. ACM downshifts coding and/or modulation tocompensate for the degradation. Accordingly, the interference detector204 in step 518 may evaluate whether SNR is greater than or equal to anSNR threshold SNR_Th. If so, then the interference detector 204 in step520 may evaluate whether ACM is enabled and in step 522 whether therehas been a negative ACM change. If so, then the interference detector204 in step 524 may determine that an external interferer is probable,and then may proceed to run validation algorithms. If ACM in step 520 isnot enabled, then the interference detector 204 in step 526 may evaluatewhether the Far End ATPC has been enabled. If in step 526 theinterference detector 204 determines that the Far End ATPC has beenenabled or in step 522 the interference detector 204 determines thatthere has not been a negative ACM change, then the interference detector204 in step 528 computes the Far End Power Adjustment. In step 530, theinterference detector 204 determines whether the computed PowerAdjustment is greater than a Power Adjustment Threshold. If so, then theinterference detector 204 in step 524 may determine that an externalinterferer is probable, and then may proceed to run validationalgorithms. If SNR is less than the SNR Threshold, or the radio linkconfiguration does not have any compensation mechanisms enabled, or theFar End Power Adjustment is less than the Power Adjustment Threshold,then the interference detector 204 may default to evaluating theperformance affecting interference B criteria, discussed below. Thistype of interference is not explicit and can easily go unnoticed.

Performance-affecting interference type B—When the radio link hasdegraded due to the interference but below the severity level ofgenerating errors, and when the radio link configuration does not havecompensation mechanisms enabled or the interference is too low totrigger any compensation action, the interference detector 204 may use amore sensitive set of parameters based on the U-BER. The U-BERidentifies how hard the Forward Error Correction decoder is working toclean the received signal, e.g., how many errors are being corrected inevery FEC frame that goes across the receiver. The more errors beingcorrected, the more likely that the PTP system 100 will reach a pointwhere it cannot correct them all in a given FEC frame and thus will havean uncorrectable frame. Although it uses a similar criterion as the SNR,U-BER is considerably more sensitive and allows the system to detectdegradation even before the SNR starts degrading. In some embodiments,the interference detector 204 in step 532 computes the change in U-BER,and in step 534 determines whether the change in U-BER is greater thanor equal to an U-BER Threshold (U-BER_Th). If so, then the interferencedetector 204 in step 536 determines that an external interferer isprobable, and proceeds to run validation algorithms. If not, then theinterference detector 204 determines that, for the record of parameterscollected during the current instance in time, the radio link was notbeing affected or at least not being affected significantly enough by aninterferer to be detected. This type of interference is not explicit andcan easily go unnoticed.

If at least one of the degradation conditions is met, the interferencedetection system 126 may proceed with validation processes to validateand/or classify the type of interference and/or whether the detectedinterference may be considered a false positive. The interferencedetection system 126 may consider the following validation factors:

-   -   1. Persistence—The interference detection system 126 validates        the duration of interference, thus enabling determination of        false positives, short single interference bursts, burst        interferers that are constantly affecting the radio link, and/or        steady interferers.    -   2. Multipath—Using the processes noted above with regard to FIG.        4, the interference detection system 126 validates if the type        of interference may be due to multipath.    -   3. Symmetry—The interference detection system 126 validates if        the same degradation pattern is happening in both directions of        the radio link. If the degradation is symmetric, external        interference is unlikely as it is usually not symmetric in        nature.    -   4. Historical references and regular/irregular behavior—The        interference detection system 126 validates against data for        this radio link from the historical database, e.g., to determine        if the interference pattern is happening at regular intervals or        if it is showing irregular behavior. This information may be        used as part of the analysis that should lead to a corrective        action.

Details of the validation processes will be discussed below.

FIG. 6 is a flowchart illustrating a method 600 of validating a detectedinterference based on interference persistence (interference duration)and classifying false positives, single burst interference, burstcontinuous interference and steady interferers, in accordance with someembodiments of the present invention.

The validation/classification engine 206 may evaluate interferencepersistence. In some embodiments, the validation/classification engine206 evaluates consecutive samples (forward in time) from a moment aninterferer is detected. If the detected condition is no longer present,then the validation/classification engine 206 may track interference asit improves or worsens and ultimately detect when the interferencestops.

In step 602, the validation/classification engine 206 determines if thedetected condition remains present. If so, then thevalidation/classification engine 206 in step 604 updates a persistencecounter and proceeds to exit. If not, then validation/classificationengine 206 proceeds to step 606.

In step 606, the validation/classification engine 206 determines if thedetected condition has degraded. If the condition has degraded, thevalidation/classification engine 206 in step 608 logs the degradation inthe historical database 210 (possibly with the assistance of the datastorage engine 208), in step 610 updates the detected condition, andproceeds to step 604 to update the persistence counter. If the conditionhas not degraded, the validation/classification engine 206 in step 612determines whether the condition has improved but interference stillremains present. If so, then the validation/classification engine 206 instep 614 logs the improvement, and proceeds to step 610 to update thedetected condition and to step 604 to update the persistence counter.

If the original condition has improved and interference is no longerpresent, then the validation/classification engine 206 in step 616clears the original condition, and in step 618 determines whether theduration of the original condition is less than the minimum interferencethreshold. If so, then the validation/classification engine 206 in step620 logs a potential false positive. Since an interferer may be presentfor an indefinite period of time, the validation/classification engine206 may implement a boundary condition to stop metering the interferenceduration once it crosses a predefined limit. Thevalidation/classification engine 206 may wait for a minimum number ofsamples without interference before the validation/classification engine206 declares the radio link interference free. This will create a levelof hysteresis to reduce toggling conditions. In some embodiments, thevalidation/classification engine 206 identifies interferers having ashort duration, e.g., only one or two samples long, as false positives.Short interferences may be triggered by anomalies in measurement orglitches in the sampling process. Although the validation/classificationengine 206 may not send an alarm to a link operator when a falsepositive is determined, the validation/classification engine 206 mayrecord the occurrence of the false positive to determine in the futureif there exists a recurring pattern.

If the duration of the original condition is greater than or equal tothe minimum interference threshold, then the validation/classificationengine 206 in step 622 logs the persistence duration (e.g., thepersistence counter value), and in step 624 determines whether thepersistence duration is greater than a steady threshold. If not, thenthe validation/classification engine 206 in step 626 classifies theinterference as a single burse interference and logs the single burstinterference.

If the interference duration is greater than the steady threshold, thenthe validation/classification engine 206 in step 628 determines whetherthe interference variation is greater than an interference variationthreshold. If so, then the validation/classification engine 206 in step632 classifies the interference as a continuous burst interference andlogs the continuous burst interference. If not greater than theinterference variation threshold, then the validation/classificationengine 206 in step 630 classifies the interference as a steadyinterferer and logs the steady interferer.

The validation/classification engine 206 identifies interference thatcontinuously affects the radio link over a longer duration while the SNR(or any other link performance degradation parameter) is showing anoscillating pattern of several dB as a burst interference. This will berepresented as a predetermined larger duration threshold. In someembodiments, the validation/classification engine 206 may be unable todetect a burst interference due to the severity level of theinterference, especially if the radio link is lost. Further, thevalidation/classification engine 206 classifies an interference with along duration and constant or relatively constant intensity thattranslates into a steady degradation of SNR (or any other linkperformance degradation parameter) as a steady interference.

FIG. 7 is a flowchart illustrating a method of discriminating anexternal interference from multipath interference, in accordance withsome embodiments of the present invention. In some embodiments, thevalidation/classification engine 206 may evaluate one or both of twoconfigurations, namely, when the configuration includes a spacediversity (SD) link and/or when it does not. Accordingly, in step 702,the validation/classification engine 206 determines whether the link isa space diversity link.

In the space diversity case, the validation/classification engine 206 instep 704 presumes that both receivers will not be affected at the sametime, when the interference is due to multipath. So, in someembodiments, the validation/classification engine 206 tracks theinterference in a first receiver over a number of consecutive samplesand in a second receiver over a number of consecutive samples. Thevalidation/classification engine 206 expects the second receiver to beunaffected after the interference stops in the first receiver, andexpects within a predetermined amount of time the second receiver tostart showing the effects of the interference and then to eventuallydisappear. If the validation/classification engine 206 does not detectthose conditions, e.g., the condition is present in both receivers, thenthe validation/classification engine 206 in step 708 may determine thatthe interference is due to an external interferer. If thevalidation/classification engine 206 in step 706 detects thoseconditions, e.g., the condition is not present in the second receiver,then the validation/classification engine 206 may determine that theinterference is due to multipath. The validation/classification engine206 in step 710 verifies the condition over time, namely, in step 716determines whether the condition worsens or remains constant in thefirst receiver and then goes away, in step 718 determines that, whilethe condition is bad in the receiver, the second receiver has an SNRthat remains good, and in step 720 determines that, while the firstreceiver condition improves or clears the second receiver deteriorates.In step 712, the validation/classification engine 206 determines whetherthe three conditions were met. If not, then thevalidation/classification engine 206 proceeds to step 708 to determinethat the interference is unlikely due to multipath. If all threeconditions were met, then the validation/classification engine 206 instep 714 determines the interference is likely due to multipath.

In the non-space diversity case, the validation/classification engine206 in step 722 monitors for an interference that it detects in step 724as present in the receiver for only a predetermined amount of time andthen disappears (same as in the space diversity case). Thevalidation/classification engine 206 in step 726 determines whether thecondition has been confirmed. If not, then the validation/classificationengine 206 proceeds to step 708 and determines that multipathinterference is unlikely. If the condition is present, then, because thePTP system 100 does not have a second receiver to confirm the multipathcondition, the validation/classification engine 206 in step 728 verifieshistorical reference to cyclic behavior or modem coefficients indicativeof multipath. That is, the validation/classification engine 206 maydepend on one or more of the following:

-   -   1. The cyclical nature of multipath—Multipath may be due to        naturally occurring phenomena that occur when natural events        take place, like the tide coming in or out of a particular        seashore. To identify a multipath condition, the        validation/classification engine 206 in step 728 may use records        in the historical database 210 for the radio link to determine        whether a repetitive interference pattern coincides with the        naturally occurring phenomena. In some embodiments, different        naturally occurring events may occur with several hours of each        other such that the different event types can cause different        interference patterns. In some embodiments, the        validation/classification engine 206 in step 728 may use records        from the historical database 210 for the radio link to identify        the patterns of the different events.    -   2. Use of additional modem coefficients—The        validation/classification engine 206 in step 728 may evaluate        equalizer coefficients detected during the interference and may        compare the detected coefficients with ones collected after the        interference is gone. The validation/classification engine 206        may identify an equalizer coefficient pattern when the type of        interference is due to multipath, as the equalizer will try to        align the two signals to compensate for it.

If the validation/classification engine 206 in step 730 confirms amultipath condition using the above tests, then thevalidation/classification engine 206 in step 732 classifies theinterference as multipath. If the validation/classification engine 206cannot confirm a multipath condition using the above tests, then thevalidation/classification engine 206 may classify the interference ascaused by an external interferer. If the validation/classificationengine 206 cannot confirm a multipath condition but detects sufficientevidence that it is possible, then the validation/classification engine206 may report the event as an external interferer but flag it in thehistorical database 210 as potentially multipath in case the informationcan be used to confirm it or a different event in the future.

It will be appreciated that there may be relationships between thetechniques used to detect multipath and the tests used to detectpersistence. In some embodiments, the validation/classification engine206 may skip performing the multipath process if the interferencepersistence process shows that the interference type is either a steadyor continuous burst.

FIG. 8 is a flowchart illustrating a method 800 of validating a detectedinterference based on symmetry, in accordance with some embodiments ofthe present invention.

External interference in PTP radio links are usually asymmetric. Byvalidating that substantially the same degradation pattern is happeningin both directions of the radio link, the validation/classificationengine 206 may flag the event only as a probable interferer (notconfirmed) and may record the probable interferer event as such in thehistorical database 210 for the radio link. By flagging the probableinterferer event as such, the validation/classification engine 206 maybe able to confirm the event in the future, e.g., if a future interfererevent in this radio link are asymmetrical.

To determine if the interference is symmetric, thevalidation/classification engine 206 in step 802 correlates theinterference analysis in the near end receiver with the sameinterference analysis in the far end receiver. Thevalidation/classification engine 206 preferably conducts thiscorrelation using samples from the same temporal snapshot. If the nearend interference condition is different than the far end interferencecondition, then the validation/classification engine 206 in step 804logs the asymmetry and a probable external interferer. If the near endinterference condition is substantially the same as the far endinterference condition, then the validation/classification engine 206 instep 806 logs the symmetry and the unlikelihood of an externalinterferer.

FIG. 9 is a flowchart illustrating a method 900 of validating a detectedinterference based on regular/irregular patterns identified in thehistorical database 210, in accordance with some embodiments of thepresent invention.

The historical database 210 stores the different conditions detected inthe radio link over time. In some embodiments, thevalidation/classification engine 206 evaluates records in the historicaldatabase 210 to determine if interference is repeating at regular orirregular intervals or patterns. When looking for a specific pattern,the validation/classification engine 206 may, in different embodiments,look at a different number of past records and/or a different amount ofelapsed time. The validation/classification engine 206 may look forlunar patterns, seasonal patterns, weather patterns, time of daypatterns, etc.

As described herein, the validation/classification engine 206 can searchthe historical database 210 to determine if the type of interference isattributable to multipath in non-space diversity links and to trackthose links that are labeled as having probable interference due to itsoriginal detection showing symmetric behavior. Thevalidation/classification engine 206 may use the information as part ofthe analysis that could lead to a corrective action. Thevalidation/classification engine 206 may use the information to enhancethe link and network health reports.

In step 902, the validation/classification engine 206 searches therecords of the historical database 210. The validation/classificationengine 206 in step 904 identifies the occurrence of similar and/orequivalent interference conditions. When the validation/classificationengine 206 in step 904 identifies only one occurrence, thevalidation/classification engine 206 classifies and logs theinterference as irregular. When the validation/classification engine 206in step 904 identifies more than one occurrence, thevalidation/classification engine 206 in step 908 evaluates the timeinterval of the occurrence (or compares the timing with weather recordsor other patterns) to attempt to establish a pattern (or correlation).If the validation/classification engine 206 detects a pattern in step910, the validation/classification engine 206 in step 912 classifies andlogs the interference as regular. If the validation/classificationengine 206 does not detect a pattern in step 910, then thevalidation/classification engine 206 proceeds to step 906 to classifyand log the interference as irregular.

FIG. 10 is a flowchart illustrating a method of triggering performanceof the main method 500 based on condensed information, in accordancewith some embodiments of the present invention.

The condensed evaluation engine 212 can use condensed information toscreen which radio links may be showing signs of degradation due tointerference during a time period. The condensed evaluation engine 212may store condensed information in bins that keep track of maximum andminimum levels of certain link performance parameters during eachspecific period of time associated with the bin. In some embodiments,the condensed evaluation engine 212 may maintain 15-minute bins thatrecord maximum and minimum levels for important link performanceparameters like RSL, SNR, ES, SES, U-BER, etc. In some embodiments, thecondensed evaluation engine 212 may evaluate the data within the15-minute bins to determine the possibility of an external interferencehaving occurred within that time period.

Although the bins are being described as containing informationcorresponding to a 15-minute window of time, the bins can contain anylength of time, albeit in some embodiments longer than a number oftemporal snapshots that exceeds the likelihood of temporal correlationof radio parameters. Accordingly, condensed information alone may beinsufficient to confirm whether interference is present during aspecified period of time, because the values stored in the bins are nottime correlated with each other. In other words, in some embodiments,the interference detection system 126 cannot guarantee that when a lowSNR value is detected in a bin, its corresponding RSL value was high orlow at the time. Such conditions may both be happening within the samebin, but not necessarily in the same temporal snapshot.

In some embodiments, the condensed evaluation engine 212 may onlytrigger the more detailed interference analysis of the main method 500when there is enough evidence in a bin to suggest that a potentialinterferer may be present. That way, the interference detection system126 may avoid unnecessarily wasting system resources and increasingcomputational costs.

In some embodiments, the condensed evaluation engine 212 starts in step1002 by selecting a bin. The condensed evaluation engine 212 in step1004 checks if the maximum RSL level of the bin never exceeded thepre-determined RSL threshold. If so, then the condensed evaluationengine 212 in step 1006 may presume that there has been a fadingcondition during the whole time period. If the condensed evaluationengine 212 in step 1004 detects a maximum RSL level that exceeded theRSL threshold for any portion of the time period, the condensedevaluation engine 212 may proceed to check for link degradationconditions.

As in the main method 500, the condensed evaluation engine 212 may checkthe more severe interference conditions, e.g., in step 1008 using minSNR equal to zero as an indicator of the link losing lock and in step1012 ES and/or SES increments as an indicator of errors being generated.If the condensed evaluation engine 212 detects any of these more severeinterference conditions in the condensed information, with the RSL beinghigh enough at least for a portion of the bin, the condensed evaluationengine 212 in step 1010 determines a very high likelihood of an externalinterference and triggers execution of the main method 500 using thedetailed data for that radio link and over that specific time period.

The condensed evaluation engine 212 may check the less severeinterference conditions, e.g., in step 1014 low SNR values as anindicator of link performance degradation and in step 1018 the maximumU-BER value being high enough to indicate link performance degradation.If the condensed evaluation engine 212 detects any of these conditionsin the condensed information, with the RSL being high enough at leastfor a portion of the bin, the condensed evaluation engine 212 in step1016 determines a likelihood of an external interference and triggersexecution of the main method 500 using the detailed data for that radiolink and over that specific time period.

If the condensed evaluation engine 212 does not detect a likelihood ofan external interferer, the condensed evaluation engine 212 maydetermine that there is a low likelihood of an external interference,and returns to step 1002 to evaluate another bin.

In some embodiments, when the condensed evaluation engine 212 detects apossible external interference based on the parameters of a bin, thecondensed evaluation engine 212 may cause interference detection of theradio link in real time, in addition to and/or instead of a detailedevaluation of the radio link within the time period associated with thebin.

FIG. 11 is a block diagram illustrating details of a computer system1100. Any of the systems, engines, databases, and/or networks describedherein may comprise an instance of one or more computer systems 1100. Insome embodiments, functionality of the computer system 1100 is improvedto the perform some or all of the functionality described herein. Thecomputer system 1100 comprises a processor 1102, memory 1104, storage1106, a communication network interface 1108, and an input/output (I/O)interface 1110, communicatively coupled to a communication channel 1114.The processor 1102 is configured to execute executable instructions(e.g., programs). In some embodiments, the processor 1102 comprisescircuitry or any processor capable of processing the executableinstructions.

The memory 1104 stores data. Some examples of memory 1104 includestorage devices, such as RAM, ROM, RAM cache, virtual memory, etc. Invarious embodiments, working data is stored within the memory 1104. Thedata within the memory 1104 may be cleared or ultimately transferred tothe storage 1106.

The storage 1106 includes any storage configured to retrieve and storedata. Some examples of the storage include flash drives, hard drives,optical drives, cloud storage, and/or magnetic tape. Each of the memory1104 and the storage 1106 comprises a computer-readable medium, whichstores instructions or programs executable by the processor 1102.

The I/O interface 1110 may include any device that inputs data (e.g.,mouse and keyboard) and any device that outputs data (e.g., a speaker ordisplay).

The communication network interface 1108 may support communication overan Ethernet connection, a serial connection, a parallel connection,and/or an ATA connection. The communication network interface 1108 mayalso support wireless communication (e.g., 802.11 db/g/n, WiMax, LTE,WiFi). It will be apparent that the communication network interface 1108may support many wired and wireless standards. The communication networkinterface 1108 may be coupled to a network (e.g., computer network 128)via the link 1112.

The elements of the computer system 1100 are not limited to thosedepicted in FIG. 11. A computer system 1100 may comprise more or lesshardware, software and/or firmware components than those depicted (e.g.,drivers, operating systems, touch screens, biometric analyzers, and/orthe like). Further, elements may share functionality and still be withinvarious embodiments described herein. For example, encoding and/ordecoding may be performed by the processor 1102 and/or a co-processorlocated on a GPU (i.e., NVidia).

It will be appreciated that the terms “engine”, “system” “module” and/or“database” may comprise software, hardware, firmware, and/or circuitry.In one example, one or more software programs comprising instructionscapable of being executable by a processor may perform one or more ofthe functions of the engines, databases, modules or systems describedherein. In another example, circuitry may perform the same or similarfunctions. Alternative embodiments may comprise more, less, orfunctionally equivalent engines, systems, modules or databases, andstill be within the scope or present embodiments. For example, thefunctionality of the various systems, engines, modules and/or databasesmay be combined or divided differently. The databases may include cloudstorage. It will further be appreciated that the term “or” as usedherein may be construed in either an inclusive or exclusive sense.Moreover, plural instances may be provided for resources, operations, orstructures described herein as a single instance.

The database described herein may be any suitable structure (e.g., anactive database, a relational database, a self-referential database, atable, a matrix, an array, a flat file, a documented-oriented storagesystem, a non-relational No-SQL system, and the like), and may becloud-based or otherwise.

The systems, methods, engines, modules, and/or databases describedherein may be at least partially processor-implemented, with aparticular processor or processors being an example of hardware. Forexample, at least some of the operations herein may be performed by oneor more processors or processor-implemented engines. Moreover, the oneor more processors may also operate to support performance of therelevant operations in a “cloud computing” environment or as a “softwareas a service” (SaaS). For example, at least some of the operations maybe performed by a group of computers (as examples of machines includingprocessors), with these operations being accessible via a network (e.g.,the Internet) and via one or more appropriate interfaces (e.g., anApplication Program Interface (API)).

The performance of certain of the operations may be distributed amongthe processors, not only residing within a single machine, but deployedacross a number of machines. In some example embodiments, the processorsor processor-implemented engines may be located in a single geographiclocation (e.g., within a home environment, an office environment, or aserver farm). In other example embodiments, the processors orprocessor-implemented engines may be distributed across a number ofgeographic locations.

Throughout this specification, plural instances may implementcomponents, operations, or structures described as a single instance.Although individual operations of one or more methods are illustratedand described as separate operations, one or more of the individualoperations may be performed concurrently, and nothing requires that theoperations be performed in the order described and/or illustrated.Structures and functionality presented as separate components in exampleconfigurations may be implemented as a combined structure or component.Similarly, structures and functionality presented as a single componentmay be implemented as separate components. These and other variations,modifications, additions, and improvements fall within the scope of thesubject matter herein.

The table below lists abbreviations that may have been used in thisdocument.

Term Description ACM Adaptive Coding and Modulation ATPC Automatictransmit power control BER Bit Error Rate/Bit Error Ratio dB Decibel,logarithmic unit of signal ratio dBm Decibel referenced to 1 mW DNLDemodulator not locked alarm ES Errored Seconds FDD Frequency DivisionDuplexing FE Far End - Usually referring to the other side of a radiolink FEC Forward Error Correction IDU In Door Unit NE Near End - Usuallyreferring to the local side of the radio link NMS Network ManagementSystem ODU Out Door Unit QAM Quadrature Amplitude Modulation QPSKQuaternary (Quadraphase) Phase Shift Keying RBER Residual Bit Error RateRSL Receive signal level, in units of dBm SES Severely Errored SecondsSNR Signal to Noise Ratio TDD Time Division Duplexing U-BER Uncoded BitError Rate

The foregoing description of the preferred embodiments of the presentinvention is by way of example only, and other variations andmodifications of the above-described embodiments and methods arepossible in light of the foregoing teaching. Although the network sitesare being described as separate and distinct sites, one skilled in theart will recognize that these sites may be a part of an integral site,may each include portions of multiple sites, or may include combinationsof single and multiple sites. The various embodiments set forth hereinmay be implemented utilizing hardware, software, or any desiredcombination thereof. For that matter, any type of logic may be utilizedwhich is capable of implementing the various functionality set forthherein. Components may be implemented using a programmed general purposedigital computer, using application specific integrated circuits, orusing a network of interconnected conventional components and circuits.Connections may be wired, wireless, modem, etc. The embodimentsdescribed herein are not intended to be exhaustive or limiting. Thepresent invention is limited only by the following claims.

The invention claimed is:
 1. An interference detection system in apoint-to-point radio system, the point-to-point radio system including afirst site in radio communication with a second site, comprising: atleast one processor; and memory storing computer instructions, thecomputer instructions when executed by the at least one processorcausing the system to perform, gathering a temporal snapshot of radioparameter values associated with at least a first site of apoint-to-point radio system, the radio parameter values including atleast a receive signal level (RSL) value and at least one other radioparameter value correlated with signal degradation during the temporalsnapshot; determining whether the RSL value is greater than an RSLthreshold; determining whether the at least one other radio parametervalue indicates a threshold level of signal degradation during thetemporal snapshot; at least when the RSL value is greater than the RSLthreshold and the at least one other radio parameter value indicates athreshold level of signal degradation during the temporal snapshot, thendetermining that external interference is likely present during thetemporal snapshot; at least when the RSL value is not greater than theRSL threshold, then determining that the external interference is likelynot present during the temporal snapshot; and performing a responsiveaction to a determination of the external interference being likelypresent during the temporal snapshot.
 2. The interference detectionsystem of claim 1, wherein the radio parameter values include radioparameter values associated with a modem and a radio frequency unit atthe first site during the temporal snapshot.
 3. The interferencedetection system of claim 1, wherein the at least one other radioparameter value includes a Demodulator Not Locked (DNL) Alarm, andwherein the at least one other radio parameter value indicates athreshold level of signal degradation at least when the DNL Alarm isactive.
 4. The interference detection system of claim 1, wherein the atleast one other radio parameter value includes Errored Seconds (ES) orSeverely Errored Seconds (SES) value, and wherein the at least one otherradio parameter value indicates a threshold level of signal degradationat least when the ES or SES value is increasing from a previous sample.5. The interference detection system of claim 1, wherein the at leastone other radio parameter value includes a signal-to-noise ratio (SNR)value, and wherein the at least one other radio parameter valueindicates a threshold level of signal degradation at least when at leastthe SNR value is less than a threshold.
 6. The interference detectionsystem of claim 1, wherein the at least one other radio parameter valueincludes a change in an Uncoded Bit Error Rate (U-BER), and wherein theat least one other radio parameter value indicates a threshold level ofsignal degradation at least when the change in the U-BER is greater thana threshold.
 7. The interference detection system of claim 1, whereinthe at least one other radio parameter includes Adaptive Code Modulation(ACM) data, and wherein the at least one other radio parameter valueindicates a threshold level of signal degradation at least when ACM isactive and negative.
 8. The interference detection system of claim 1,wherein the at least one other radio parameter value includes AutomaticTransmit Power Control (ATPC) data, and wherein the at least one otherradio parameter value indicates a threshold level of signal degradationat least when ATPC is enabled and a power adjustment is greater than athreshold.
 9. The interference detection system of claim 1, wherein thecomputer instructions when executed by the processor further cause thesystem to perform evaluating interference persistence; and determining afalse positive at least when the interference persistence is less than aminimum threshold duration.
 10. The interference detection system ofclaim 9, wherein the computer instructions when executed by theprocessor further cause the system to perform determining an amount ofinterference variation; identifying the external interference as asteady interferer at least when the amount of interference variation isless than a threshold; and identifying the external interference as acontinuous bursty interferer at least when the amount of interferencevariation is greater than the threshold.
 11. The interference detectionsystem of claim 1, wherein the computer instructions when executed bythe processor further cause the system to perform determining firstinterference effects on a first receiver at the first site in spacediversity with a second receiver at the first site; determining secondinterference effects on the second receiver at the first site; comparingthe first interference effects with the second interference effects; andat least when the first interference effects are substantially the sameas the second interference effects, then validating the externalinterference.
 12. The interference detection system of claim 1, whereinthe computer instructions when executed by the processor further causethe system to perform determining first SNR on a first receiver at thefirst site in space diversity with a second receiver at the first site;determining second SNR on the second receiver; and at least when thefirst SNR indicates signal degradation while the second SNR does notindicate signal degradation and when thereafter the first SNR improvesor clears while the second SNR deteriorates, then identifying theexternal interference as a likely multipath interference.
 13. Theinterference detection system of claim 1, wherein the computerinstructions when executed by the processor further cause the system toperform comparing a near-end interference condition with a far-endinterference condition; and at least when the near-end interferencecondition is not substantially similar to the far-end interferencecondition, the validating the external interference.
 14. Theinterference detection system of claim 1, wherein the computerinstructions when executed by the processor further cause the system toperform searching a historical database for records indicative of aninterference pattern or correlation with external events; and using theinterference pattern or correlation with external events to assist inidentifying future interferences as not being due to an externalinterferer.
 15. The interference detection system of claim 1, whereinthe computer instructions when executed by the processor further causethe system to perform gathering a bin of radio parameter information,the bin of radio parameter information including maximum and minimumlevels of RSL values and the at least one other radio parameter valueoccurring during a specific time period; and evaluating the bin of radioparameter information to determine a likelihood of the externalinterference occurring in any temporal snapshot within the specific timeperiod, before performing an analysis of any temporal snapshot of radioparameter values within the specific time period.
 16. The interferencedetection system of claim 15, wherein the specific time period includesa 15-minute time period.
 17. An interference detection method in apoint-to-point radio system, the point-to-point radio system including afirst site in radio communication with a second site, comprising:gathering a temporal snapshot of radio parameter values associated withat least a first site of a point-to-point radio system, the radioparameter values including at least a receive signal level (RSL) valueand at least one other radio parameter value correlated with signaldegradation during the temporal snapshot; determining whether the RSLvalue is greater than an RSL threshold; determining whether the at leastone other radio parameter value indicates a threshold level of signaldegradation during the temporal snapshot; at least when the RSL value isgreater than the RSL threshold and the at least one other radioparameter value indicates a threshold level of signal degradation duringthe temporal snapshot, then determining that external interference islikely present during the temporal snapshot; at least when the RSL valueis not greater than the RSL threshold, then determining that theexternal interference is likely not present during the temporalsnapshot; and performing a responsive action to a determination of theexternal interference being likely present during the temporal snapshot.18. The interference detection method of claim 17, further comprisingevaluating interference persistence; and determining a false positive atleast when the interference persistence is less than a minimum thresholdduration.
 19. The interference detection method of claim 18, furthercomprising determining an amount of interference variation; identifyingthe external interference as a steady interferer at least when theamount of interference variation is less than a threshold; andidentifying the external interference as a continuous bursty interfererat least when the amount of interference variation is greater than thethreshold.
 20. The interference detection method of claim 17, furthercomprising determining first interference effects on a first receiver atthe first site in space diversity with a second receiver at the firstsite; determining second interference effects on the second receiver atthe first site; comparing the first interference effects with the secondinterference effects; and at least when the first interference effectsare substantially the same as the second interference effects, thenvalidating the external interference.
 21. The interference detectionmethod of claim 17, further comprising determining first SNR on a firstreceiver at the first site in space diversity with a second receiver atthe first site; determining second SNR on the second receiver; and atleast when the first SNR indicates signal degradation while the secondSNR does not indicate signal degradation and when thereafter the firstSNR improves or clears while the second SNR deteriorates, thenidentifying the external interference as a likely multipathinterference.
 22. The interference detection method of claim 17, furthercomprising comparing a near-end interference condition with a far-endinterference condition; and at least when the near-end interferencecondition is not substantially similar to the far-end interferencecondition, the validating the external interference.
 23. Theinterference detection method of claim 17, further comprising searchinga historical database for records indicative of an interference patternor correlation with external events; and using the interference patternor correlation with external events to assist in identifying futureinterferences as not being due to an external interferer.
 24. Theinterference detection method of claim 17, further comprising gatheringa bin of radio parameter information, the bin of radio parameterinformation including maximum and minimum levels of RSL values and theat least one other radio parameter value occurring during a specifictime period; and evaluating the bin of radio parameter information todetermine a likelihood of the external interference occurring in anytemporal snapshot within the specific time period, before performing ananalysis of any temporal snapshot of radio parameter values within thespecific time period.